Influence of organophilic clay and preparation methods on EVA/montmorillonite nanocomposites

Ethylene‐vinyl acetate copolymer (EVA)/montmorillonite MMT nanocomposites have been prepared by using different methods: one is from the organophilic montmorillonite (OMT) and the other is from the pristine MMT and reactive compatibilizer hexadecyl trimethyl ammonium bromide (C16). In this study, different kneaders were used (twin‐screw extruder and twin‐roll mill) to prepare nanocomposites. The nanocomposite structures are evidenced by the X‐ray diffraction (XRD) and high‐resolution electronic microscope (HREM). The thermal properties of the nanocomposites were investigated by thermogravimetric analysis (TGA). Moreover, the tensile tests were carried out with a Universal testing machine DCS‐5000. It is shown that different methods and organophilic montmorillonite have influence on EVA/MMT nanocomposites.© 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 2416–2421, 2004     

Thermal and combustion behavior of ethylene‐vinyl acetate/aluminum trihydroxide/Fe‐montmorillonite composites

The flammability characterization and synergistic flame‐retardant effect of Fe‐montmorillonite (Fe‐OMT) in the ethylene‐vinyl acetate/aluminum hydroxide (EVA/ATH) compounds were studied using limiting oxygen index (LOI), UL‐94 test, cone calorimeter, microscale combustion calorimetry (MCC), and thermogravimetric analysis (TGA). The results showed that addition of Fe‐OMT increases the LOI value and improves the UL 94 rating. Cone calorimeter data indicate that the addition of Fe‐OMT greatly reduced the heat release rate and carbon monoxide production rate. Furthermore a compact char residue formed on the surface of the sample with a suitable of Fe‐OMT during the combustion. The MCC results indicate that addition of Fe‐OMT reduced the heat release rate and catalyzed the decomposition of EVA. The TGA data showed further evidence that Fe‐OMT can catalyze carbonization reactions. POLYM. ENG. SCI., 2012. © 2011 Society of Plastics Engineers     

Structural characterization of LDPE/EVA blends containing nanoclay‐flame retardant combinations

The combination of different types of organo‐modified montmorillonite (MMT) with aluminum hydroxide (aluminum trihydrate—ATH), as a flame retardant system for polyethylene‐ethylene vinyl acetate (LDPE/EVA), blends were studied. Five different types of organically modified montmorillonite clays, each with different modifier, were used. The structural characterization was carried out by X‐ray diffraction (XRD) and scanning electron microscopy in transmission mode (STEM). The mechanical and rheological properties were also evaluated. The XRD analysis showed a clear displacement of the d₀₀₁ signal, which indicates a good degree of intercalation, especially for the MMT‐I28 and MMT‐20, from Nanocor and Southern Clay Products, respectively. The presence of ATH and the compatibilizer did not have any effect on the exfoliation of the studied samples. The thermal stability and flame retardant properties were evaluated by thermogravimetric analysis (TGA), limiting oxygen index (LOI—ASTM D2863), and flammability tests (Underwriters Laboratory—UL‐94). The effect of different compatibilizers on the clay dispersion and exfoliation was studied. The results indicated that the addition of montmorillonite makes it possible to substitute part of the ATH filler content while maintaining the flame retardant requirements. The thermal stability of MMT/ATH‐filled LDPE/EVA blends presented a slight increase over the reference ATH‐filled LDPE/EVA blend. Compositions with higher clay content (10 wt %) showed better physicochemical properties. The increased stability of the higher clay content compositions results from the greater inorganic residual formation; this material has been reported to impart better performance in flammability tests. The mechanical properties and flame retardancy remained similar to those of the reference compound. The reduced ATH content resulted in lower viscosities and densities, facilitating the processing of the polymer/ATH/clay compounds. Extrusion of these compounds produced a lower pressure in the extrusion head and required reduced electrical power consumption. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Thermal stability and flame retardance properties of acrylonitrile-butadiene-styrene/polyvinyl chloride/organophilic Fe-montmorillonite nanocomposites

In the article, acrylonitrile-butadiene-styrene/polyvinyl chloride/organophilic Fe-montmorillonite (ABS/PVC/Fe-OMT) nanocomposites were prepared by melt intercalation method. In order to determine if the presence of iron ion in the structure of organophilic montmorillonite (OMT) lattice can affect thermal, flame retardance and smoke suppressant properties in the ABS/PVC blends. ABS/PVC/organophilic natural montmorillonite (Na-OMT) nanocomposites were prepared as the comparable sample. Fe-MMT and Na-MMT were treated by cetyl trimethylammonium bromide (CTAB). The information on morphologies and structures of ABS/PVC/OMT nanocomposites was obtained using X-ray diffraction (XRD) and transmission electron microscopy (TEM). The thermal properties of the nanocomposites were characterized by thermogravimetric analysis, and flame retardant properties were obtained via limiting oxygen index (LOI), UL-94 vertical burning test and smoke density. The nanocomposites, based on Fe-OMT, exhibited better flame retardance, better smoke suppressant properties, and lower degradation degree than those of pure ABS/PVC blends and the ABS/PVC/Na-OMT nanocomposites.     

Thermal Properties and Flammability of Ethylene-Vinyl Acetate Copolymer/Montmorillonite/Polyethylene Nanocomposites with Flame Retardants

Ethylene-vinyl acetate copolymer (EVA)/montmorillonite (MMT) composite was blended with a linear low density polyethylene (LLDPE). X-ray diffraction and transmission electron microscopy (TEM) image of the EVA/MMT composite are in support of an intercalated with partially delaminated nanocomposite. The tensile strength of the nanocomposite is about 20% higher than that without layered silicates, MMT. Furthermore, the incorporation of MMT into polymer blend delays the main thermo-oxidative degradation. Cone calorimeter test points out that the addition of layered silicates into the pristine EVA/LLDPE blend or the blend with a low smoke non-halogen (LSNH) fire retardants, aluminum trihydroxide, and antimony trioxide, can reduce the maximum heat release rate by 30–40%. The smoke suppressing effect of layered silicates is only observed in the nanocomposite containing flame retardants. According to the limiting oxygen index (LOI) data and cone calorimeter test, the addition of the nanodispersed layered silicate and LSNH flame retardants to the EVA/LLDPE exhibits a synergistic effect on the flame retardancy and smoke suppression.     

Structural effects of type of intercalant in poly (4‐vinylpyridine) nanocomposites: compatible homopolymer or block copolymer

4‐vinylpyridine monomer was mixed with organophilic montmorillonite (MMT) clay and polymerized in the presence of free‐radical initiator. MMT clay was rendered organophilic by means of ion‐exchanging sodium cations for low‐molecular‐weight quaternized poly(4‐vinylpyridine) (P4VP) homopolymer and diblock copolymers of styrene and quaternized 4‐vinylpyridine (SVP) with different sequence lengths. The swelling behaviour of the MMT clay was studied by X‐ray diffraction (XRD). After the cation exchange, the resulting organophilic clays showed an expansion of interlayer distance indicating the nanoscale ordering of intercalant polymer and MMT layers. The nanocomposite materials, when moulded, exhibited improved thermal stability and dynamic mechanical properties compared with neat P4VP. The composite, having longer ionic segments in its organophilic MMT, showed exfoliated nanocomposite structure as well as higher stiffness and damping properties at higher temperatures even for MMT loading as low as 2 wt%. Copyright © 2006 Society of Chemical Industry     

Ethylene propylene diene terpolymer/ethylene vinyl acetate/layered silicate ternary nanocomposite by solution method

A new ternary nanocomposite has been developed using ethylene propylene diene terpolymer (EPDM), ethylene vinyl acetate (EVA‐45) copolymer, and organically modified layered silicate (16 Me‐MMT) from sodium montmorillonite (Na⁺‐MMT). Wide angle X‐ray diffraction and transmission electron microscopic analysis confirmed the intercalation of the polymer chains in between the organosilicate layers and the nanoscale distribution of 16 Me‐MMT in polymer matrix, respectively. The measurement of mechanical properties for 2–8 wt% of 16 Me‐MMT loadings showed a significant increase in tensile strength, elongation at break, and modulus at different elongations. Such an improvement in mechanical properties has been correlated based on the fracture behavior of nanocomposite by SEM analysis. Thermal stability of EPDM/EVA/layered silicate ternary nanocomposites also showed substantial improvements compared with the neat EPDM/EVA blend, confirming thereby the formation of a high performance nanocomposite. POLYM. ENG. SCI., 46:437–843, 2006. © 2006 Society of Plastics Engineers     

Synthesis and characterization of polyvinyl acetate/montmorillonite nanocomposite by in situ emulsion polymerization technique

Exfoliated polyvinyl acetate/montmorillonite nanocomposite (PVAc/MMT) was prepared via in situ emulsion polymerization. The resulting PVAc with various organophilic MMT contents was investigated. In the nanocomposite latex preparation, sodium lauryl sulfate (SLS), ammonium persulfate (APS), and poly (vinyl alcohol) (PVA) are used as anionic emulsifier, conventional anionic initiator, and stabilizer, respectively. The samples were characterized using elemental analysis, X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), atomic force microscopy (AFM). The XRD and AFM results demonstrate that the MMT well dispersed at molecular level in the PVAc matrix. Thermal properties of the nanocomposite were studied by using differential scanning calorimetric analysis (DSC). The exfoliated PVAc/MMT nanocomposite showed a higher glass transition temperature and a better thermal stability compared to the pure PVAc.     

Morphology,thermal, and mechanical properties of flame‐retardant silicone rubber/montmorillonite nanocomposites

Flame‐retardant methyl vinyl silicone rubber (MVMQ)/montmorillonite nanocomposites were prepared by solution intercalation method, using magnesium hydroxide (MH) and red phosphorus (RP) as synergistic flame‐retardant additives, and aero silica (SiO₂) as synergistic reinforcement filler. The morphologies of the flame‐retardant MVMQ/montmorillonite nanocomposites were characterized by environmental scanning electron microscopy (ESEM), and the interlayer spacings were determined by small‐angle X‐ray scattering (SAXS). In addition to mechanical measurements and limited oxygen index (LOI) test, thermal properties were tested by thermogravimetric analysis (TGA). The decomposition temperature of the nanocomposite that contained 1 wt % montmorillonite can be higher (129°C) than that of MVMQ as basal polymer matrix when 5% weight loss was selected as measuring point. This kind of silicone rubber nanocomposite is a promising flame‐retardant polymeric material. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 99: 3275–3280, 2006     

Synergistic flame retardant effects of Fe-OMMT with LDH in EVA/LDH composites

Abstract

The synergistic effects of Fe organic modified montmorillonite (Fe-OMMT) with layered double hydroxides (LDHs) in ethylene vinyl acetate copolymer/LDH (EVA/LDH) composites have been studied using thermal analysis [thermogravimetric analysis (TGA)], limiting oxygen index (LOI), UL-94 test and cone calorimeter test (CCT). The results showed that the addition of a given amount of Fe-OMMT apparently increased the LOI value and the rating in the UL-94 test. The results from the LOI and UL-94 tests show that Fe-OMMT can act as flame retardant synergistic agents in EVA/LDH composites. The CCT data indicated that the addition of Fe-OMMT in the EVA/LDH system can greatly reduce the heat release rate. The TGA data show that Fe-OMMT, as an excellent flame retardant synergist of LDH, cannot increase the thermal degradation temperature and the charred residues.     

Flame retardancy of nanocomposites

Nishizawa Technical Institute (NTI) and Kyoto Institute of Technology (KIT) have developed EVA‐clay nanocomposites with excellent mechanical and flame retardant properties by a reactive process and have succeeded in a novel method to synthesize an aluminium hydroxide nanoparticle, which has the effect of improving the flame retardancy of nanocomposites with EVA. About the EVA‐clay nanocomposites, the peak heat release rate (HRR) of sample MM2 (EVA‐clay partially processed nanocomposites) and sample MM3 (EVA‐clay completely processed nanocomposites) was reduced from 1/3 (one third) to 1/4 (one fourth) compared with EVA only. Sample AL‐1 (EVA‐aluminium nanocomposites) showed a more effective reduction of HRR than sample AL‐2 (EVA‐normal aluminium hydroxide). Beside these experiments, the orientation of the nanofiller MMT (montmorillonite) by a 2‐axis extruder equipped a special novel kneading roll head and the flame retardancy of silica nanocomposite coating materials (Sol‐Gel process) is discussed. Copyright © 2004 John Wiley & Sons, Ltd.     

Effect of clay modification on the morphological,mechanical, and thermal properties of polyamide 6/polypropylene/montmorillonite nanocomposites

Polyamide 6/polypropylene (PA6/PP = 70/30 parts) blends containing 4 phr (parts per hundred resin) of organophilic montmorillonite (OMMT) were prepared by melt compounding. The sodium montmorillonite (Na‐MMT) was modified using three different types of alkyl ammonium salts, namely dodecylamine, 12‐aminolauric acid, and stearylamine. The effect of clay modification on the morphological and mechanical properties of PA6/PP nanocomposites was investigated using x‐ray diffraction (XRD), transmission electron microscopy (TEM), tensile, flexural, and impact tests. The thermal properties of PA6/PP nanocomposites were characterized using thermogravimetric analysis (TGA), dynamic mechanical analysis (DMA), and heat distortion temperature (HDT). XRD and TEM results indicated the formation of exfoliated structure for the PA6/PP nanocomposites prepared using stearylamine modified montmorillonite. On the other hand, a mixture of intercalated and exfoliated structures was found for the PA6/PP nanocomposites prepared using 12‐aminolauric acid and dodecylamine modified montmorillonite. Incorporation of OMMT increased the stiffness but decreased the ductility and toughness of PA6/PP blend. The PA6/PP nanocomposite containing stearylamine modified montmorillonite showed the highest tensile, flexural, and thermal properties among all nanocomposites. This could be attributed to better exfoliated structure in the PA6/PP nanocomposite containing stearylamine modified montmorillonite. The storage modulus and HDT of PA6/PP blend were increased significantly with the incorporation of both Na‐MMT and OMMT. The highest value in both storage modulus and HDT was found in the PA6/PP nanocomposite containing stearylamine modified montmorillonite due to its better exfoliated structure. POLYM. COMPOS., 31:1156–1167, 2010. © 2009 Society of Plastics Engineers     

The effectiveness of magnesium carbonate‐based flame retardants for poly(ethylene‐co‐vinyl acetate) and poly(ethylene‐co‐ethyl acrylate)

In this report we outline recent work on the evaluation of magnesium carbonate‐based flame retardants for polymers commonly used in halogen‐free flame retardant wire and cable applications: poly(ethylene‐co‐vinyl acetate) (EVA) and poly(ethylene‐co‐ethyl acrylate) (EEA). Natural magnesium carbonate (magnesite), synthetic magnesium carbonate (hydromagnesite), and hydromagnesite/huntite blends were combined with EVA or EEA and tested for flame retardancy effectiveness with the cone calorimeter. The flammability results showed that the effectiveness of these carbonates was polymer dependent, suggesting that polymer degradation chemistry played a role in the flammability reduction mechanism. Hydromagnesites were, in general, more effective in reducing flammability, being comparable in performance to magnesium hydroxide. Finally, we report some polymer–clay (organically treated montmorillonite and magadiite) + magnesium carbonate flame retardant results which showed that the nanocomposite yielded mixed results. Specifically, the polymer–clay nanocomposite samples did not always yield the greatest reductions in peak heat release rate. Copyright © 2007 John Wiley & Sons, Ltd.     

Flame retardancy and thermal stability of ethylene-vinyl acetate copolymer nanocomposites with alumina trihydrate and montmorillonite

The development of fire retardant for wire and cable sheathing materials has oriented toward low smoke and halogen-free flame retardant technology to achieve better safety for electrical equipment and devices and to satisfy standards. However, many polymer flame resistance materials require a very high proportion of metal hydrate filler within the polymer matrix (60 wt%) to achieve a suitable level of flame resistance, which may lead to inflexibility, poor mechanical properties and problems during compounding and processing. In this study, the alumina trihydrate (ATH) was added to montmorillonite (MMT) as the halogen-free flame retardant of ethylene-vinyl acetate (EVA) copolymer, with various ratios of EVA/ATH/MMT. The prepared nanocomposites were characterized through various techniques of XRD, tensile test, DSC analysis, TGA, LOI evaluation, and FE-SEM to explore the effects of organic modified clay (OMMT) and the layer distance on the mechanical, thermal, and flame resistance properties. In the XRD examinations, the layer-distance of MMT increased from 1.27 to 1.96 nm when polymer was added to the octadecylamine modified MMT. The best tensile strength was obtained at 3 wt% MMT. In addition, the halogen-free flame resistance grade of EVA containing 3 wt% OMMT and 47 wt% ATH revealed the best elongation and fire resistance (LOI = 28). The tensile and flame resistance properties of the nanocomposites were also significantly improved.     

Effect of both silane‐grafted and ion‐exchanged organophilic clay in structural,thermal, and mechanical properties of unsaturated polyester nanocomposites

Unsaturated polyester (UPE) resin including styrene monomer was mixed with organophilic montmorillonite (MMT) clay and its crosslinking polymerization reaction was done in the presence of free‐radical initiator. MMT clay was modified with cetyl trimethly ammonium bromide and trimethoxy vinyl silane. The nanocomposites were characterized by X‐ray diffraction (XRD), atomic force microscopy (AFM), scanning electron microscopy (SEM), thermogravimetric and dynamic mechanical analyses (TGA and DMA). The exfoliated nanocomposite structure was obtained when the MMT clay was modified in the presence of both modifiers, whereas individual modifications all resulted in intercalated structures. The exfoliated UPE nanocomposite exhibited better thermal and dynamic mechanical properties when compared with pure UPE and other composites, even with 3 wt% clay loading. POLYM. COMPOS., 2010. © 2009 Society of Plastics Engineers     

A polymeric flame retardant and surfactant‐free montmorillonite nanocomposites: Preparation and exfoliation mechanism discussion

A polymeric flame retardant (PDEPD) and various amounts of sodium montmorillonite (Na‐MMT) nanocomposites with exfoliation structure were prepared via one‐step polycondensation, attempting to prepare flame‐retardant nanocomposites. The nanocomposites exhibited high thermal stability at high temperature. Based on several comparative studies, we investigated and proposed the possible exfoliation mechanism of Na‐MMT in PDEPD substrate. The microscale combustion calorimeter and cone calorimeter results showed the PDEPD/Na‐MMT nanocomposites could significantly improve the flame retardancy of polystyrene and polyurethane elastomer (TPU), especially the TPU matrix. This study provides new viewpoint for preparing flame‐retardant nanocomposites without surfactants. POLYM. COMPOS., 35:167–173, 2014. © 2013 Society of Plastics Engineers     

Preparation and Combustion Properties of Flame Retardant Nylon 6/Montmorillonite Nanocomposite

Flame retardant Nylon 6 (PA6)/montmorillonite (MMT) nanocomposites have been prepared using direct melt intercalation technique by blending PA6, organophilic clay and conventional fire retardants, such as the melamine cyanurate (MCA) and the combination of decabromodiphenyl oxide (DB) and antimony oxide (AO). Their morphology and combustion properties are characterized by XRD, transmission electron microscopy (TEM), UL‐94 test and Cone Calorimeter experiments. The flame retardant nanocomposites with MCA or DB and AO show lower heat release rate (HRR) peak compared to that of conventional flame retardant PA6. Meanwhile, the synergetic effect was studied between clay and DB‐AO.

TEM of PA‐n nanocomposite.     

Effects of an (Intumescent flame retardant)‐montmorillonite combination on the thermal stability and fire‐retardant properties of LDPE/EVA nanocomposites

The combined effects of an organically modified montmorillonite (OMMT) and an intumescent flame retardant, poly (piperazine spirocyclic pentaerythritol bisphosphonate) (PPSPB), in (low‐density polyethylene)/[ethylene‐(vinyl acetate) copolymer] (LDPE/EVA) nanocomposites were observed. The results from X‐ray diffraction and transmission electron microscopy studies showed that exfoliated LDPE/EVA/PPSPB/OMMT nanocomposites were formed. Thermal stability and flammability properties were investigated by thermogravimetric analysis and cone calorimeter tests. The combination of PPSPB and montmorillonite improved thermal stability and reduced significantly the flammability, including peak heat release rate (PHRR), total heat release, average mass loss rate, etc. The PHRR of LDPE/EVA/PPSPB/OMMT was reduced by about 50% compared to that of an LDPE/EVA blend. The morphology and composition of the residues generated by cone calorimeter tests were investigated by scanning electronic microscopy (SEM) and energy dispersive X‐ray (EDX) analysis. The results of SEM showed that a compact and dense intumescent char was formed from the LDPE/EVA/PPSPB/OMMT nanocomposite upon combustion. The results of EDX examination revealed that the carbon content of this char was increased significantly by the combined effect of PPSPB and montmorillonite. J. VINYL ADDIT. TECHNOL., 19:285–292, 2013. © 2013 Society of Plastics Engineers     

Preparation and characterization of transparent poly(methyl methacrylate)/Na+‐MMT nanocomposite films by solution casting

Films of poly(methyl methacrylate) (PMMA)/sodium montmorillonite (Na⁺‐MMT) nanocomposites have been successfully prepared utilizing Na⁺‐MMT by N,N‐dimethylformamide solution casting. The nanocomposite films show high transparency, enhanced thermal resistance, and mechanical properties in comparison with the neat polymer film. The transparency of the films was investigated by UV‐vis spectra. The exfoliated dispersion of Na⁺‐MMT platelets in nanocomposites were investigated by X‐ray diffraction and transmission electron microscopy. The enhanced thermal resistance and mechanical properties of PMMA were studied by thermal gravimetric analysis and dynamic mechanical analysis, respectively. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

耐辐射无卤阻燃线缆材料的制备

将氢氧化镁/红磷/乙烯-醋酸乙烯共聚物(EVA)体系作为无卤阻燃材料主体,通过加入蒙脱土(MMT)和耐辐射助剂共混制备复合材料,以减小红磷用量,降低成本,增强材料的阻燃性能和耐辐射性能。重点考察了蒙脱土对复合材料的拉伸性能、阻燃性能、加工流动性的影响。另一方面,研究了双酚类抗氧剂对材料耐辐射性能的影响。结果表明,材料的拉伸性能、阻燃性能、耐辐射性能达到核电站线缆要求。